Certain conventional vehicles are provided with distance sensors to help the driver in situations of poor visibility, for example when he must reverse park. In certain conventional vehicles, a sound signal is emitted with a frequency as high as the vehicle is close to an obstacle. The driver must then himself estimate the braking force which should be applied. In other known vehicles, the distance measured by the distance sensors is used by a controller to automatically brake the vehicle. However, intervention by the driver is still necessary. In case of an incorrect manoeuvre, the vehicle can strike an obstacle and be damaged. This risk is particularly great in the case of maneuvering on a sloping surface with little free space around the vehicle. In fact, a gradient of 2 to 3% is sufficient to put a car in motion if it is not braked.
A vehicle is known from DE-4 201 806 comprising a distance sensor measuring the distance between the vehicle and an obstacle situated behind the vehicle. When this distance is less than a determined threshold, a control unit activates a pump which increases the pressure of the hydraulic brakes in orders to stop the vehicle.
A lorry is also known from US2003/0111902 including a distance sensor measuring the distance between the lorry and an unloading platform situated behind the lorry. The lorry also includes a velocity sensor. A control unit stores in its memory a minimum profile and a maximum profile defining, for a given distance, a velocity range in which the velocity of the lorry must be situated. If this is not the case, the control unit sends control pulses to a pressure valve to increase or reduce the pressure of the hydraulic brakes of the lorry so that the lorry is automatically stopped against the unloading platform. When the lorry has stopped, the hydraulic pressure is maintained for some seconds. If the engine is switched off, the pressure cannot be maintained. In this case, the driver must manually engaged the parking brake for the lorry to be kept in position. Should the driver forget to do this, if the lorry is on a sloping surface it can be displaced in the direction of the slope and strike an obstacle.